**Course Title:** Modern C++ Programming: Mastering C++ with Best Practices and Advanced Techniques **Section Title:** Multithreading and Concurrency **Topic:** Introduction to multithreading in C++ with the `<thread>` library. **Introduction** Multithreading is a fundamental concept in modern programming that allows developers to write efficient and concurrent code. In this topic, we will explore the basics of multithreading in C++ using the `<thread>` library, which provides a high-level interface for creating and managing threads. **What is Multithreading?** Multithreading is a programming technique that enables a program to execute multiple threads or flows of execution concurrently. This allows a program to perform multiple tasks simultaneously, improving responsiveness, throughput, and overall system performance. **The `<thread>` Library** The `<thread>` library was introduced in C++11 as a part of the C++ Standard Library. It provides a set of classes and functions that allow developers to create and manage threads in a portable and efficient manner. **Creating a Thread** To create a thread in C++, you need to include the `<thread>` header file and use the `std::thread` class. The `std::thread` class takes a callable object, such as a function or a lambda expression, as its constructor argument. Here's an example of creating a thread that executes a simple function: ```cpp #include <thread> #include <iostream> void printHello() { std::cout << "Hello from thread!" << std::endl; } int main() { // Create a thread that executes the printHello() function std::thread t(printHello); // Wait for the thread to finish t.join(); return 0; } ``` In this example, the `printHello` function is executed by a separate thread, while the main thread waits for the thread to finish using the `join()` function. **Thread States** A thread can be in one of the following states: * **Running**: The thread is currently executing. * **Waiting**: The thread is waiting for a condition to occur or a resource to become available. * **Blocked**: The thread is blocked due to a synchronization primitive (e.g., mutex, condition variable). * **Finished**: The thread has finished executing and has returned from its entry point. * **Detached**: The thread is detached from the parent thread and is running independently. **Thread Functions** The `std::thread` class provides several functions that can be used to manipulate threads: * `join()`: Waits for the thread to finish and then returns. * `detach()`: Detaches the thread from the parent thread. * `hardware_concurrency()`: Returns the number of concurrent threads that can be executed by the hardware. **Example: Concurrent Execution** Here's an example of using multiple threads to execute multiple tasks concurrently: ```cpp #include <thread> #include <iostream> void printNumbers(int start, int end) { for (int i = start; i <= end; ++i) { std::cout << i << std::endl; } } int main() { // Create two threads that print numbers concurrently std::thread t1(printNumbers, 1, 10); std::thread t2(printNumbers, 11, 20); // Wait for both threads to finish t1.join(); t2.join(); return 0; } ``` In this example, two threads are created that execute two separate instances of the `printNumbers` function concurrently. **Best Practices and Guidelines** Here are some best practices and guidelines for using multithreading in C++: * Use `std::thread` instead of platform-specific threading APIs. * Use `std::mutex` and `std::lock_guard` to protect shared resources. * Avoid using `std::detach()` unless necessary. * Use `std::join()` or `std::try_join()` to wait for threads to finish. * Avoid using `std::thread::native_handle()` unless necessary. **Conclusion** In this topic, we've explored the basics of multithreading in C++ using the `<thread>` library. We've learned how to create and manage threads, synchronize access to shared resources, and execute tasks concurrently. In the next topic, we'll dive deeper into synchronization primitives such as mutexes, condition variables, and locks. **References:** * [The `<thread>` Library](https://en.cppreference.com/w/cpp/thread) **Leave a comment below with your thoughts on this topic! Ask for help if you have any questions.** **What's next?** In the next topic, we'll explore **Synchronization primitives: Mutexes, condition variables, and locks**.